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Heavy-metal hot subdwarfs (sdB and sdO) represent a small group of stars withunusually high concentrations of trans-iron elements in their atmospheres,having abundances ~ 10000 times solar. One example is LS IV-14$^{\circ}$ 116,where a number of heavy-metal absorption lines of Sr II, Y III and Zr IV havebeen observed in the optical band 4000 - 5000 A. We use a fully relativisticDirac atomic R-Matrix (DARC) to calculate photoionization cross sections ofSr$^{0}$, Y$^{+}$ and Zr$^{2+}$ from their ground state to the twentiethexcited level. We use the cross sections and the oscillator strengths tosimulate the spectrum of a hot subdwarf. We obtain complete sets ofphotoionization cross sections for the three ions under study. We use thesedata to calculate the opacity of the stellar atmospheres of hot subdwarf stars,and show that for overabundances observed in some heavy-metal subdwarves,photo-excitation from zirconium, in particular, does contribute some backwarming in the model.

Opacity modelling of heavy-metal hot subdwarfs. Photoionization of Sr$^0$, Y$^{+}$ and Zr$^{2+}$